A combat logistics patrol of more than 40 vehicles drives down a desert road during a convoy conducted by Marines with Combat Logistics Regiment 2, Regional Command (Southwest), in southern Helmand province, Afghanistan, on Sept. 29, 2013. The Marines conducted logistical operations for four days before finally returning to Camp Leatherneck, Afghanistan. (Cpl. Paul Peterson / Marines Corps)

Marines may be forced to leave military equipment behind in Afghanistan if delays in signing a bilateral security agreement stretch into late spring or summer, the commandant of the Marine Corps warned Tuesday.

Afghan President Hamid Karzai has resisted heavy pressure from the Defense Department to sign the agreement, even though it was been approved by the Loya Jirga — the Afghanistan National Grand Council — in November, saying he wants his successor to sign it after the national elections in April.

The agreement would confirm the way forward for the U.S. in Afghanistan after the projected end of combat operations at the close of this year, including the possibility of leaving a force of 10,000 troops in country to assist local military and civilian security efforts. But the uncertainty that exists until the agreement is finalized has tied the hands of U.S. commanders in the short term.

At a think tank event in Washington, D.C., Gen. Jim Amos said he knows he can get his Marines out by the 2014 deadline, regardless of delays, but has concerns about the valuable gear that remains in country.

“Ideally, what you’d want to do do is on December the 31st, the last piece of equipment is loaded on an airplane or loaded on a truck and it’s headed down to Karachi (a Pakistani port that serves as a key U.S. supply hub). The last Marine gets on a plane and flies out on December 31st,” Amos said. “It’s never gonna work that way. There is physics involved, and you’re not only moving people, but stuff.”

Amos said he doesn’t know what the cutoff date is for when the Corps will have to plan to leave equipment behind, but he worries that the timeline will continue to slide toward the end of 2014 if the BSA remained unsigned until after the election.

“I think with enough airplanes and enough movement, you can get everybody out,” he said. “But it would not be ideal. I worry about the equipment.”

Amos did not say how much or what kinds of equipment might be left behind. Marine logistics officials announced previously that most of the Corps’ 1,200 mine-resistant, ambush-protected vehicles will not travel back to the U.S. from Afghanistan, as the Defense Department is thinning its inventory of the bulky land vehicles. In an effort to save them from the scrap heap, the Pentagon recently announced it was giving away 13,000 of the vehicles to allied partners and U.S. police departments.

The Marines have already moved 75 percent of all their equipment out of Afghanistan, Amos said, with a force of just 4,400 Marines remaining in Regional Command Southwest. And while drawdown and security efforts continue, he said he doesn’t expect to see significant changes in conditions on the ground between now and the end of 2014.

“My sense is, it’s about as good as it’s going to get,” Amos said. “When I talk to people about Afghanistan, I don’t say winning or losing. I never use those terms. But what I do say is that I am confident that by December of this year that we will have set the conditions for the greatest opportunity for the people of Helmand and Nimroz provinces to succeed.”

Afghanistan remains a “dangerous part of the world,” Amos said, but with the Marines’ work in assisting Afghan police forces and helping district officials to set up local governance, he is optimistic about the Afghans’ chances of maintaining security gains on their own.

“I think we will have done everything we can by this December,” Amos said. “So I feel good about it. I want to see Afghanistan succeed, maybe not to my standards, but to the standards that work for them.”